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          <th colspan="3" align="center">Chapter 2. 
		Upgrading from previous versions of Berkeley DB
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            <h2 class="title"><a id="upgrade_process"></a>Chapter 2. 
		Upgrading from previous versions of Berkeley DB
        </h2>
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      <p>
    The following information describes the general process of upgrading Berkeley DB installations.
    There are four areas to be considered when upgrading Berkeley DB applications and database
    environments: the application API, the database environment's region files, the underlying
    database formats, and, in the case of transactional database environments, the log files.  The
    upgrade procedures required depend on whether or not the release is a major or minor release (in
    which either the major or minor number of the version changed), or a patch release (in which
    only the patch number in the version changed).  Berkeley DB major and minor releases may
    optionally include changes in all four areas, that is, the application API, region files,
    database formats, and log files may not be backward-compatible with previous releases.
</p>
      <p>
    Each Berkeley DB major or minor release described in this book has a chapter indicating how to
    upgrade to the new release.  The chapter describes any API changes made in the release.
    Application maintainers should review the API changes and update their applications as necessary
    before recompiling with the new release.  In addition, each chapter includes a section specifying
    whether the log file format or database formats changed in non-backward-compatible ways as part
    of the release.  Because there are several underlying Berkeley DB database formats, and they do
    not all necessarily change in the same release, changes to a database format in a release may
    not affect any particular application.  Further, database and log file formats may have changed
    but be entirely backward-compatible, in which case no upgrade will be necessary.
</p>
      <p>
    A Berkeley DB patch release will never modify the API, regions, log files, or database formats
    in incompatible ways, and so applications need only be relinked (or, in the case of a shared
    library, pointed at the new version of the shared library) to upgrade to a new release.  Note
    that internal Berkeley DB interfaces may change at any time and in any release (including patch
    releases) without warning.  This means the library must be entirely recompiled and reinstalled
    when upgrading to new releases of the library because there is no guarantee that modules from
    one version of the library will interact correctly with modules from another release.  We
    recommend using the same compiler release when building patch releases as was used to build the
    original release; in the default configuration, the Berkeley DB library shares data structures
    from underlying shared memory between threads of control, and should the compiler re-order
    fields or otherwise change those data structures between the two builds, errors may result.
</p>
      <p>
    If the release is a patch release, do the following:
</p>
      <div class="orderedlist">
        <ol type="1">
          <li>
            <p>
        Shut down the old version of the application.
    </p>
          </li>
          <li>
            <p>
        Install the new version of the application by relinking or installing a new version of the
        Berkeley DB shared library.
    </p>
          </li>
          <li>
            <p>
        Restart the application.
    </p>
          </li>
        </ol>
      </div>
      <p>
    Otherwise, if the application <span class="bold"><strong>does not</strong></span> have a Berkeley DB
    transactional environment, the application may be installed in the field using the following
    steps:
</p>
      <div class="orderedlist">
        <ol type="1">
          <li>
            <p>
        Shut down the old version of the application.
    </p>
          </li>
          <li>
            <p>
        Remove any Berkeley DB environment using the <a href="../api_reference/C/envremove.html" class="olink">DB_ENV-&gt;remove()</a> method or an appropriate system
        utility.
    </p>
          </li>
          <li>
            <p>
        Recompile and install the new version of the application.
    </p>
          </li>
          <li>
            <p>
        If necessary, upgrade the application's databases.  See 
        <a href="../programmer_reference/am_upgrade.html" class="olink">Database upgrade</a>
        for more information.
    </p>
          </li>
          <li>
            <p>
        Restart the application.
    </p>
          </li>
        </ol>
      </div>
      <p>
    Otherwise, if the application has a Berkeley DB transactional environment, but neither the log
    file nor database formats need upgrading, the application may be installed in the field using
    the following steps:
</p>
      <div class="orderedlist">
        <ol type="1">
          <li>
            <p>
        Shut down the old version of the application.
    </p>
          </li>
          <li>
            <p>
        Run recovery on the database environment using the <a href="../api_reference/C/envopen.html" class="olink">DB_ENV-&gt;open()</a> method or the <a href="../api_reference/C/db_recover.html" class="olink">db_recover utility</a>.
    </p>
          </li>
          <li>
            <p>
        Remove any Berkeley DB environment using the <a href="../api_reference/C/envremove.html" class="olink">DB_ENV-&gt;remove()</a> method or an appropriate system
        utility.
    </p>
          </li>
          <li>
            <p>
        Recompile and install the new version of the application.
    </p>
          </li>
          <li>
            <p>
        Restart the application.
    </p>
          </li>
        </ol>
      </div>
      <p>
    If the application has a Berkeley DB transactional environment, and the log files need upgrading
    but the databases do not, the application may be installed in the field using the following
    steps:
</p>
      <div class="orderedlist">
        <ol type="1">
          <li>
            <p>
        Shut down the old version of the application.
    </p>
          </li>
          <li>
            <p>
        Still using the old version of Berkeley DB, run recovery on the database environment using
        the <a href="../api_reference/C/envopen.html" class="olink">DB_ENV-&gt;open()</a> method, or the <a href="../api_reference/C/db_recover.html" class="olink">db_recover utility</a>.
    </p>
          </li>
          <li>
            <p>
        If you used the <a href="../api_reference/C/envopen.html" class="olink">DB_ENV-&gt;open()</a> method to run recovery, make sure that the Berkeley DB environment
        is removed using the <a href="../api_reference/C/envremove.html" class="olink">DB_ENV-&gt;remove()</a> method or an appropriate system utility. 
    </p>
          </li>
          <li>
            <p>
        Archive the database environment for catastrophic recovery using
        the <code class="literal">db_archive</code> utility as described in the
        <a href="../programmer_reference/transapp_archival.html" class="olink">Database and log file archival</a> section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
    </p>
          </li>
          <li>
            <p>
        Recompile and install the new version of the application.
    </p>
          </li>
          <li>
            <p>
        Force a checkpoint using the <a href="../api_reference/C/txncheckpoint.html" class="olink">DB_ENV-&gt;txn_checkpoint()</a> method or the <a href="../api_reference/C/db_checkpoint.html" class="olink">db_checkpoint utility</a>. If you use the
        <a href="../api_reference/C/db_checkpoint.html" class="olink">db_checkpoint utility</a>, make sure to use the new version of the utility; that is, the version that
        came with the release of Berkeley DB to which you are upgrading.
    </p>
            <p>
        Note that forcing a checkpoint might result in warning messages
        about log files that are being skipped. This is normal, and can be
        safely ignored.
    </p>
          </li>
          <li>
            <p>
        Remove unnecessary log files from the environment using the <code class="literal">-d</code> option on
        the <a href="../api_reference/C/db_archive.html" class="olink">db_archive utility</a>, or from an application which calls the <a href="../api_reference/C/logarchive.html" class="olink">DB_ENV-&gt;log_archive()</a> method with the
        <a href="../api_reference/C/logarchive.html#archive_DB_ARCH_REMOVE" class="olink">DB_ARCH_REMOVE</a> flag.
    </p>
            <p>
        Note that removing log files in this way might result in warning messages
        about log files that are being skipped. This is normal, and can be
        safely ignored.
    </p>
            <p>
        Note that if you are upgrading a replicated application, then you should
        <span class="emphasis"><em>not</em></span> perform this step until all of the replication sites have been
        upgraded to the current release level. If you run this site before all your sites are
        upgraded, then errors can occur in your replication activities because important version
        information might be lost.
    </p>
          </li>
          <li>
            <p>
        Restart the application.
    </p>
          </li>
        </ol>
      </div>
      <p>
    Otherwise, if the application has a Berkeley DB transactional environment and the databases need
    upgrading, the application may be installed in the field using the following steps:
</p>
      <div class="orderedlist">
        <ol type="1">
          <li>
            <p>
        Shut down the old version of the application.
    </p>
          </li>
          <li>
            <p>
        Still using the old version of Berkeley DB, run recovery on the database environment using
        the <a href="../api_reference/C/envopen.html" class="olink">DB_ENV-&gt;open()</a> method, or the <a href="../api_reference/C/db_recover.html" class="olink">db_recover utility</a>.
    </p>
          </li>
          <li>
            <p>
        If you used the <a href="../api_reference/C/envopen.html" class="olink">DB_ENV-&gt;open()</a> method to run recovery, make sure that the Berkeley DB environment
        is removed using the <a href="../api_reference/C/envremove.html" class="olink">DB_ENV-&gt;remove()</a> method or an appropriate system utility. 
    </p>
          </li>
          <li>
            <p>
        Archive the database environment for catastrophic recovery using
        the <code class="literal">db_archive</code> utility as described in the
        <a href="../programmer_reference/transapp_archival.html" class="olink">Database and log file archival</a> section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
    </p>
          </li>
          <li>
            <p>
        Recompile and install the new version of the application.
    </p>
          </li>
          <li>
            <p>
        Upgrade the application's databases.  See
        <a href="../programmer_reference/am_upgrade.html" class="olink">Database upgrade</a>
        for more information.
    </p>
          </li>
          <li>
            <p>
        Archive the database for catastrophic recovery again (using different media than before, of
        course).  Note: This archival is not strictly necessary.  However, if you have to perform
        catastrophic recovery after restarting the application, that recovery must be done based on
        the last archive you have made.  If you make this second archive, you can use it as the
        basis of that catastrophic recovery.  If you do not make this second archive, you have to
        use the archive you made in step 4 as the basis of your recovery, and you have to do a full
        upgrade on it before you can apply log files created after the upgrade to it.
    </p>
          </li>
          <li>
            <p>
        Force a checkpoint using the <a href="../api_reference/C/txncheckpoint.html" class="olink">DB_ENV-&gt;txn_checkpoint()</a> method or the <a href="../api_reference/C/db_checkpoint.html" class="olink">db_checkpoint utility</a>. If you use the
        <a href="../api_reference/C/db_checkpoint.html" class="olink">db_checkpoint utility</a>, make sure to use the new version of the utility; that is, the version that
        came with the release of Berkeley DB to which you are upgrading.
    </p>
            <p>
        Note that forcing a checkpoint might result in warning messages
        about log files that are being skipped. This is normal, and can be
        safely ignored.
    </p>
          </li>
          <li>
            <p>
        Remove unnecessary log files from the environment using the <code class="literal">-d</code> option on
        the <a href="../api_reference/C/db_archive.html" class="olink">db_archive utility</a>, or from an application which calls the <a href="../api_reference/C/logarchive.html" class="olink">DB_ENV-&gt;log_archive()</a> method with the
        <a href="../api_reference/C/logarchive.html#archive_DB_ARCH_REMOVE" class="olink">DB_ARCH_REMOVE</a> flag.
    </p>
            <p>
        Note that removing log files in this way might result in warning messages
        about log files that are being skipped. This is normal, and can be
        safely ignored.
    </p>
            <p>
        Note that if you are upgrading a replicated application, then you should
        <span class="emphasis"><em>not</em></span> perform this step until all of the replication sites have been
        upgraded to the current release level. If you run this site before all your sites are
        upgraded, then errors can occur in your replication activities because important version
        information might be lost.
    </p>
          </li>
          <li>
            <p>
        Restart the application.
    </p>
          </li>
        </ol>
      </div>
      <p>
    Finally, Berkeley DB supports the live upgrade of a replication group, by allowing mixed version
    operation (replication sites running at the newer software version can inter-operate with older
    version sites).  All client sites must be upgraded first; the master site must be upgraded last.
    In other words, at all times the master must be running the lowest version of Berkeley DB.  To
    upgrade a replication group, you must:
</p>
      <div class="orderedlist">
        <ol type="1">
          <li>
            <p>
        Bring all clients up to date with the master (that is, all clients must be brought up to the
        most current log record as measured by the master's log sequence number (LSN)).
    </p>
          </li>
          <li>
            <p>
        Perform the upgrade procedures described previously on each of the individual database
        environments that are part of the replication group.  Each individual client may be upgraded
        and restarted to join the replication group.
    </p>
          </li>
          <li>
            <p>
        Shut down the master site and upgrade that site last.
    </p>
          </li>
        </ol>
      </div>
      <p>
    During live replication upgrade, while sites are running at different
    versions, you cannot add or remove sites from the replication group.
    Sites can be added or removed only after the entire group is upgraded.
</p>
      <p>
    Also, all removal of log files must be suspended throughout this entire procedure, so that there
    is no chance of a client needing internal initialization.
</p>
      <p>
    Alternatively, it may be simpler to discard the contents of all of the client database
    environments, upgrade the master database environment, and then re-add all of the clients to the
    replication group using the standard replication procedures for new sites.
</p>
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